Avian Botulism

What is Avian Botulism?

Botulism is a neuromuscular disease caused by the bacterium Clostridium botulinum. There are several different types of botulism. Type C and type E are responsible for extensive waterfowl die-offs and some fish kills. Type E is more prevalent in the Great Lakes. Botulism in humans is usually caused by type A or B and results from consuming improperly home-canned foods.

In the Great Lakes, botulism spores (the resting stage of the bacteria) are abundant in anaerobic habitats, such as soils, and aquatic sediments of many lakes. When the correct environmental factors are present, the spores germinate and begin vegetative growth of the toxin-producing bacterial cells.

An estimated 7,500 waterbirds in November 2007 and 2,900 waterbirds in 2006 died on Lake Michigan, poisoned by eating fish that carried the toxin. One theory is that infected fish, partially paralyzed by the toxin, became easy prey for flocks of migrating waterbirds. See: Upwellings March 2007 (PDF)

Scientists believe that outbreaks of type E botulism occur only when particular ecological factors happen simultaneously, such as warmer water temperatures, anoxic (oxygen deprived) conditions, and nutrient-rich substrate, or areas with large amounts of decaying plant growth. As average air and water temperatures have been rising on a global scale, warmer temperatures and anoxic conditions are occurring more frequently. Once these factors lead to the production of the toxin in food material eaten by fish, the toxin can be passed up the food chain as birds consume the infected fish.

Botulism has been identified as a problem for fish and birds in Lakes Ontario and Erie, and in Lake Michigan. For more information about avian botulism:

General Information About Botulism

Botulism in Michigan

Sources: Pennsylvania Sea Grant, Michigan Department of Natural Resources.

Contact: Mark Breederland

BOTULISM AND THE BEACH

A deadly toxin is spreading across the Great Lakes, killing fish and birds. Rebecca Williams reports scientists are trying to put the puzzle together as quickly as they can. Listen to The Environment Report

What You Can Do

Remove dead birds and fish immediately, to prevent the spread of botulism, as the bacteria in the carcasses can serve as the source of outbreaks for months. Please review the following guidelines for handling carcasses and monitoring your beach area:

  • Do not handle dead fish or birds with your bare hands.
  • Properly dispose of carcasses by double bagging and placing them in the trash.
  • Beware of fish that are floating – if they are not fighting, they are likely not healthy and should not be consumed.
  • Do not eat undercooked or improperly prepared fish or waterfowl.
  • Hunters should never harvest birds that appear to be sick or are dying.
  • Do not let your pets eat dead fish or birds.
  • Look for carcasses at two peak times: in mid-late summer and in the fall and follow proper disposal methods.

Preliminary 2007 Great Lakes Carcass Count